Using street view, you can often see "Social Security" on a building or sign.

Social Security Office Directions and Notes :

THE OFFICE IS LOCATED ONE BLOCK EAST OF LAKE AVENUE AND ONE BLOCK NORTH OF COLORADO BLVD, ON THE CORNER OF MENTOR AVE AND UNION ST.

Pasadena Social Security Office Notes

You can do things like signup for Medicare
online at ssa.gov.
Hours of Social Security offices were extended in March, 2015.
Almost all Social Security offices in the continental US have hours
of 9:00 to noon on Wednesdays, and 9:00 to 4:00 on other weekdays.
See if you can get an appointment by phone. Fridays may be less
crowded.